Geomagnetic vector measurement can effectively reduce the non-uniqueness of inversion in geophysical investigation and contribute to the qualitative and quantitative interpretation to magnetic substances. At present, the field geomagnetic measurement instruments generally adopted by geophysical prospecting workers at home and abroad include common proton magnetometers, optical pump magnetometers or Overhauser proton magnetometers. These magnetometers are convenient for use in the field, with the measurement accuracy equal or superior to 1 nT, and able to measure the scalar value of total geomagnetic intensity. However, the total-field magnetometer cannot measure the vectors of geomagnetic field. For field measurement of geomagnetic vectors, it is confined to using flux gate three-component magnetometers with lower accuracy of measurement error as large as several tens of nT. Such kind of magnetometers does not meet the requirements of professional geophysical investigation. The commercially available didD vector magnetometer, which is provided by CEM Corporation (Canada), represents the international advanced level of geomagnetic vector measurement. The measuring method adopted by didD vector magnetometer is described as follows: mount two sets of mutually orthogonal coils on the probe of a high precision total-field magnetometer, with the axial lines of the orthogonal coils normal to the geomagnetic field vector F in the horizontal plane and the meridian plane; firstly, record the total magnetic field T when bias current is not applied; subsequently, input in turn bias currents which are equivalent in value and opposite in direction in the coil whose axial line is normal to T in the meridian plane, namely the magnetic inclination (I) coil; record the composite magnetic fields resulted from the combination of the magnetic deflection field generated by these two bias currents and the geomagnetic field, which are called Ip and Im; in the same manner, input bias currents which are equivalent in value and opposite in direction in the coil whose axial line is normal to T in the horizontal plane, namely the magnetic declination (D) coil; record the composite magnetic fields resulted from the combination of the magnetic deflection field generated by these two bias currents and the geomagnetic field, which are called Dp and Dm; then, through calculation, determine the changes dl and dD in the inclination (I) and declination (D) of T (http://www.gemsys.ca/products/vecrot-magneromerets/). In the process of the measurement, it is not necessary for dIdD vector magnetometers of GME Corporation to make complete compensation to the geomagnetic components, so that the device is relatively handy. However, it is necessary to adjust in advance the axial lines of the orthogonal coils on the probe to the position to be normal to the geomagnetic vector T to be measured in the horizontal plane and the meridian plane, so the installation, adjustment and preparation of the instruments are complicated and nontrivial, and thus such instruments can only be used to measure deviation variations of geomagnetic inclination I and declination D with time in stationary Seismological and Geomagnetic observation stations. Therefore the geomagnetic vector measurement devices and technologies in the prior art are not applicable to high precision measurement in the field ore-prospecting environment.